Various toothed devices have long been disposed to cooperate with toothed carriers to achieve fiber cleaning and carding functions. In carding machines, for example, the main card drum may rotate past fixed or movable worker elements (e.g. rollers or flats) that are themselves provided with teeth or the like. Such toothed surfaces will be referred to at times herein as clothing, and the worker elements which bear them will be referred to at times herein as carding elements. The nature and size and arrangement of the teeth in the clothing are factors which are known to affect the action on the fibers being treated.
In ordinary operations heretofore it has been usual practice to install a different carding element in a carding machine when it became desirable to change the action of the clothing on the fibers. This required substantial work in removing an existing carding element, and fixing a new one in a precisely adjusted position on the machine. In view of the expense and inconvenience of such changes, it has been usual practice to keep a particular clothing in operation for a considerable time.
With the present day trend in the automation of the operating functions in spinning mills, there is a need for the optimization of cleaning effectiveness depending on a processed intermediate product (e.g. a carded sliver) or an end product (e.g. a staple fiber yarn). This is affected also by the diversity found in the fiber stocks to be processed, and the amount of fiber degradation due to working (herein referred to as fiber detriment) which is permissible in the particular operations.
The assignee of the present invention has filed Swiss Application No. CH 1929-89/1 disclosing a method for optimizing the processing of cotton in a spinning mill with regard to throughput quantity, residual dirt content and fiber detriment of the processed product and/or of the intermediate product. The subject matter of such application is incorporated herein by reference. In the present application, devices for the execution of the method are proposed. The carding elements proposed here in the present invention result in further opportunities in the realization of the aforesaid method.
The method takes into account the conditions in present day spinning mills. In earlier spinning mills, the ring spinning process was used as the only process for the manufacture of staple yarns. However, new spinning processes have been developed, which make various demands on the cleaning effectiveness and the permitted fiber detriment in the cleaning of the cotton.
With the equipment available heretofore, it has been difficult to meet optimally the various requirements with regard to the variability of the throughput quantity, the residual dirt content and the permitted fiber detriment and their relationship with each other. Optimization of the degree of cleaning to be achieved in using the aforesaid method must take into account the various high demands made on the appropriate spinning process by the last two variables mentioned. Also to be taken into consideration in connection with this optimization is the fact that the fibers presented to a spinning mill may be made up of a mixture of fibers from different origins. A mixture of this type is again an optimization of the quality demands of the finished yarn and of the economical requirements taking into account the prices of the raw cotton and the yarn.
The characteristics of cotton fibers from different origins which are affected directly by the natural features are the fineness and length of the individual fibers as well as the strength, elongation and color of the individual fibers and are affected indirectly by the type and manner of the picking, the cleanliness and the amount of dirt in the raw cotton.
The types of dirt include very coarse impurities as well as to metal parts, string, material residues and other foreign elements. There may be coarse husk fragments of the cotton and, lately, very fine husk fragments, so-called "seed coat fragments" which cause a lot of trouble in the spinning mill.
Further, as a result of the very intensive processing of the cotton fibers, fiber detriment occurs which, above all, leads to a shortening of the fibers, but which however, can also lead to a deterioration of the strength and elongation.
It is clear that in an economical cleaning department of a spinning mill an optimization must be found which meets the wishes of the commercial side for the aforesaid high performance as well as meeting the wishes of the technological side for careful opening and cleaning of the fibers. The result of this optimization can differ according to the use of the cleaned fibers in one or another of the spinning processes.